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spottopgm - convert SPOT satellite images to Portable Greymap format
spottopgm [-1|2|3] [Firstcol Firstline Lastcol Lastline] inputfile
- -1|2|3
- Extract the given colour from the SPOT image. The colours are infra-red,
visible light and ultra-violet, although I don't know which corresponds to
which number. If the image is in colour, this will be announced on standard
error. The default colour is 1.
- Firstcol Firstline Lastcol Lastline
- Extract
the specified rectangle from the SPOT image. Most SPOT images are 3000 lines
long and 3000 or more columns wide. Unfortunately the SPOT format only gives
the width and not the length. The width is printed on standard error. The
default rectangle is the width of the input image by 3000 lines.
Spottopgm
converts the named inputfile into Portable Greymap format, defaulting to
the first color and the whole SPOT image unless specified by the options.
You must edit the source program and either define BIG_ENDIAN
or LITTLE_ENDIAN, and fix the typedefs for uint32_t, uint16_t and uint8_t
appropriately.
Currently spottopgm doesn't determine the length of the
input file; this would involve two passes over the input file. It defaults
to 3000 lines instead.
Spottopgm could extract a three-color image (ppm),
but I didn't feel like making the program more complicated than it is now.
Besides, there is no one-to-one correspondence between red, green, blue and
infra-red, visible and ultra-violet.
I've only had a limited number of SPOT
images to play with, and therefore wouldn't guarantee that this will work
on any other images.
Warren Toomey wkt@csadfa.cs.adfa.oz.au
The
rest of the Pbmplus suite.
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